THE PHYLOGENETIC-RELATIONSHIPS OF BYBLIS AND RORIDULA (BYBLIDACEAE-RORIDULACEAE) INFERRED FROM PARTIAL 18S RIBOSOMAL-RNA SEQUENCES

The phylogenetic relationships of the angiosperm genera Byblis and Ror idula have been the subject of ongoing taxonomic controversy. Twenty-e ight taxa of varying degrees of alleged relationship, including 3 memb ers of the Winteraceae (as an outgroup), were investigated using parti al sequences of 18S rRNA (small subunit) and also compared against the morphological data set from HUFFORD'S (1992) cladistic treatment of 8 0 members of the Rosidae-Asteridae. The morphological analysis placed the two genera in a clade with the Sarraceniaceae in the Corniflorae-A sterid group as a sister taxon to an Ericales-Hydrangeales clade. The 18S rRNA analysis supports the recently published rbcL DNA analysis of ALBERT & al. (1992), with Roridula joined to taxa in the lower Rosida e, but Byblis joining instead to members of the Asteridae near the Sol anaceae. Comparisons for congruence between the three analyses place B yblis in the higher Asterid group near the Solanaceae, and Roridula po ssibly nearer the Sarraceniaceae and Ericales. These results imply tha t the traditional morphological characters used to relate the two gene ra are possibly the result of convergence towards similar ecological a nd life-history strategies rather than synapomorphies.